Well, what if I encountered several somebodies, and their various frameworks were self-consistent, but not the same, maybe even contradictory on some aspects? How do I choose who is more right? And that question is not even a hypothetical for me, since that is really my situation.
If they really know what they're doing than they ought not to be contradictory. That doesn't mean that they'll all be the same - different things happen for different situations, but at heart the physics is all (and must be) the same.